| Popis: |
Underwater sounds from migrating gray whales were recorded from a bottom‐mounted hydrophone array. Sound‐source locations were based upon arrival‐time differences and received levels. Visual tracking corroborated sound data. Moans were the most common of more than 231 whale sounds recorded in the presence of at least 218 whales. Moans lasted 1.5 sec; their source level was about 126 dB re 0.0002 dyn/cm2 at 1 yd; and they ranged from 20–200 Hz. Underwater blow sounds from surface exhalations were 1.25 sec long, and they ranged from 15–175 Hz. Infrequent bubble‐type signals, lasting 0.7 sec, were about 112 dB re 0.0002 dyn/cm2 at 1 yd, ranging from 15–305 Hz. Knock sounds were as high as 350 Hz at sound‐pressure levels up to 116 dB re 0.0002 dyn/cm3 at 1 yd. Gray whales were soniferous during the day and night. The average swimming speed of lone migrators was 5.5 kt, based on sound tracks. No characteristic behavior could be associated with sound production other than blow sounds during exhalations. |
